The present invention relates generally to a vehicular headlamp and, more particularly, the invention relates to a vehicular headlamp having a lens inclined with respect to an optical axis, and in which a metallic shade, provided for shielding an electric bulb so as to prevent the light from the bulb from being directed in undesired directions and functioning as a secondary light source, is prevented from deforming the lens.
In a vehicular headlamp, for example, an automobile headlamp, light emitted from an electric bulb is reflected by a reflector, and the reflected light is projected and controlled by a lens to obtain a desired light distribution pattern.
If light from the bulb is directed toward portions of the reflector other than the effective reflection region of the reflector, it is difficult to control the reflected light. Consequently, a shade has been used for shielding light which o is directed toward portions of the reflector other than the effective reflection region.
FIG. 9 shows an example of such a conventional automobile headlamp having a shade. The conventional headlamp includes an electric bulb a supported by a reflector b, a metallic shade c surrounding the electric bulb a and having an approximately cylindrical shape. The shade c is provided with a cut-out (not shown) on a side portion d thereof which allows light emitted from the bulb a and passing through the cut-out to be directed toward only the effective reflection region of the reflector b. The headlamp also has a lens e formed of a synthetic resin, which lens is inclined with respect to the direction of the optical axis X--X. With this structure, the light emitted from the electric bulb a is directed only toward the effective reflection region of the reflector b so that the light can be properly controlled by the lens e.
With the conventional automobile headlamp constructed as described above in which the lens e is inclined with respect to the direction of the optical axis X--X, since an end portion of the shade c is positioned close to the lens e, the lens may be deformed due to heat. In other words, when the bulb is lit, the shade c is heated by the bulb a to a very high temperature. Accordingly, if the shade c is positioned too close to the lens e formed of synthetic resin, the shade c, acting as a secondary heat source, may deform a part of the lens e which is closely adjacent thereto.
Heretofore, as shown in FIG. 10, there has been proposed another type of headlamp in which an end part f of a shade g has a curved shape such as circular or oblong in cross section. In this type of headlamp, the end part f of the shade g can be positioned far from the lens e compared to the former conventional shade, thus suppressing deformation of the lens e due to heat. However, there arises another problem in that the volume of the chamber surrounded by the shade g where the electric bulb a is disposed is made excessively small, as a result of which the temperature in the chamber becomes so high as to shorten the lifetime of the electric bulb a.